Create a category in WordPress
WordPress uses categories to organize your posts. You can have parent and child category making hierarchy of your posts. Enabling you to show exactly the posts you want in your navigation bar, menus, widgets etc.
To create a categories in WordPress, you need to go the Posts >> Categories
This page will allow you to create categories. First of all fill in the category Name, its slug, this will be used in the category URL, choose whether its a Parent or child category(adding a parent from the drop downs, makes it a child) add the Category Description, then click Add New Category.
To describe wordpress categories are similar to books. A book has an index of many sections and many individual pages within these sections. Categories can help you organize your web site and help your users find the information they want.
Categories are similar to this index it has many section with subsections with many pages.
A tag is specific and addresses items you discuss in a blog post. Down the line broad to specific or categories own to tags.